The male urethra is approximately 20 cm long (4 cm in the female). It is considered in three parts:
• Prostatic urethra (3 cm): bears a longitudinal elevation (urethral crest) on its posterior wall. On either side of the crest a shallow depression, the prostatic sinus, marks the drainage point for 15-20 prostatic ducts. The prostatic utricle is a 5 mm blind ending tract which opens into an eminence in the middle of the crest—the verumontanum. The ejaculatory ducts open on either side of the utricle.
• Membranous urethra (2 cm): lies in the urogenital diaphragm and is surrounded by the external urethral sphincter (sphincter urethrae).
• Penile urethra (15 cm): traverses the corpus spongiosum of the penis (see perineum, p. 59) to the external urethral meatus.
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